The present invention relates to fluid transport systems generally, and more specifically to engine fuel delivery systems.
Many turbine engines, as a result of their design, exhibit undesirable noise. For some engines this noise may include a component that manifests itself as xe2x80x9chootxe2x80x9d, having a characteristic frequency. An apparent solution to reducing this noise is to properly muffle it at its source. This, however, is often impossible without locating the root cause of the noise.
Accordingly, an improved engine, designed to exhibit less noise at identified characteristic frequency is desirable. Similarly, methods and devices capable of reducing such characteristic noise are desirable.
In accordance with the present invention, hoot noise in an engine is reduced by damping pressure fluctuations in the fuel delivery system to the engine. This may be accomplished through the use of a conduit that attenuates such pressure fluctuations. Preferably, the conduit attenuates pressure fluctuations by reflecting a portion of the pressure wave within the fluid flow so that reflected pressure waves within the flow interfere with incident pressure waves within the flow, thereby reducing the pressure fluctuations. In one embodiment, such a conduit may be formed as a quarter wave stub, in line with the fluid flow.
In accordance with an aspect of the present invention, a fuel delivery system includes a conduit for delivering fuel. The conduit has a first end and a second end extending between a first region and a second region, in which a speed of acoustic travel within the fuel differs from a speed of acoustic travel within the fuel in the conduit. The length of the conduit is equal to about an odd multiple of a quarter wave length of an acoustic wave within the fuel within the conduit, so that the wave is reflected from a boundary between the conduit and the second region to destructively interfere with an incident wave at a boundary between the first region and the conduit, and thereby reduce pressure fluctuations within the fuel.
In accordance with another aspect of the present invention, a fluid delivery system, includes a conduit for delivering generally incompressible fluid, extending from between a first region to a second region. wherein speeds of acoustic travel in the fluid in the first and second regions differ from a speed of acoustic travel in the fluid in the conduit. The conduit has; a length equal to about an odd multiple of a quarter wave length of an acoustic wave within the fluid within the conduit, so that the wave is reflected from a boundary between the conduit and the second region to destructively interfere with an incident wave within the fluid in the first region, and thereby reduce pressure fluctuations within the fluid.
In accordance with yet another aspect of the invention, a method of damping pressure variations within a fuel system of an aircraft engine, comprising determining a resonant frequency of a fluid delivery system of the engine; and including a conduit in the fluid delivery system, adapted to reflect forward travelling pressure waves within the fuel to destructively interfere with the forward travelling pressure waves within the fuel, in order to reduce pressure fluctuations in the fuel.
In accordance with a further aspect of the invention, a fluid delivery system includes a conduit having a first end and a second end extending between a first region and a second region for delivering fluid from the first region to the second region, wherein an acoustic impedance of a travelling wave within the fluid varies between the first region, the conduit, and the second region. the conduit having a length between the first end and the second end, equal to about an odd multiple of a quarter wave length of an acoustic wave of a specific frequency within the fluid within the conduit, so that the wave is reflected from a boundary between the conduit and the second region to destructively interfere with an incident wave at a boundary between the first region and the conduit, and thereby reduce pressure fluctuations within the fluid.
Other aspects and features of the present invention will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.